Body weight lb → kg

Convert body weight from lb to kg

Sources last checked: 2026-11-03

Body weight lb → kg

Convert body weight from lb to kg

Body weight (lb)

Fill in every field to see the result.

Converts units only; reference ranges depend on the laboratory, the assay and the patient.

Source: NIST Special Publication 811 (2008), Guide for the Use of the International System of Units — Appendix B.8/B.9 conversion factors: 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 mmHg = 133.322 Pa, t/°C = (t/°F − 32)/1.8.Open

What is the Body weight lb → kg?

Body weight is recorded in pounds (lb) in the USA and partly in the UK, and in kilograms in Europe, Turkey and in almost all drug-dosing references. The international pound is defined as exactly 0.45359237 kg, so the conversion is exact; rounding happens only in the result.

When to use it

Weight-based drug dosing (mg/kg) from a weight given in pounds
Calculating BMI, body surface area or predicted body weight in SI units
Reading US records, case reports or trial data

When not to use it

Weights given in stones (UK): convert to pounds first (1 st = 14 lb)
The German everyday 'Pfund' (500 g) — that is not the imperial pound

How it is calculated

kg = lb × 0.45359237

Clinical pearls and limitations

Converts units only; reference ranges depend on the laboratory, the assay and the patient.
Exact: 1 lb = 0.45359237 kg. The approximation 'divide by 2.2' is close but should not be used for narrow-margin dosing.
In paediatrics and for high-risk drugs, check that the weight on the chart is in kg; a weight entered in lb but read as kg leads to a more than twofold dose error.
Round the result sensibly (usually to one decimal place in kg); scales are not more precise.
Many dosing schemes use ideal, adjusted or lean body weight rather than actual weight — the unit conversion does not answer which weight to use.

Frequently asked questions

How do I convert pounds to kilograms?

Multiply by 0.45359237. Example: 150 lb = 68.0 kg; 220 lb = 99.8 kg.

Can I just divide by 2.2?

For a quick estimate, yes (1 kg ≈ 2.2046 lb). For dosing, use the exact factor or this calculator.

Is a German 'Pfund' the same as a pound?

No. In German everyday language, 'ein Pfund' means 500 g, while the international pound is 453.59237 g.

Evidence and guidelines

Primary source: NIST Special Publication 811 (2008), Guide for the Use of the International System of Units — Appendix B.8/B.9 conversion factors: 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 mmHg = 133.322 Pa, t/°C = (t/°F − 32)/1.8.

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For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.